recover_ethereum_keystore.js

#!/bin/node

// https://github.com/ethereumjs/ethereumjs-wallet
// -> npm install ethereumjs-wallet
var Wallet = require('ethereumjs-wallet');

var privateKey = '-> your private key here <-'; // in hex format
var keystorePassword = '-> your keystore password here <-';

var wallet = Wallet.fromPrivateKey(Buffer.from(privateKey, 'hex'));
var keystore = wallet.toV3String(keystorePassword, { n: 1024 });

console.log(keystore);